• Title/Summary/Keyword: Approximation ratio

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Comparison of the Cylindrical Geometry and the Planar Geometry for the Near-Field Radionuclides Transport Model (방사성 폐기물 처분장내 충전물질에서의 핵종 이동 모델의 원주좌표계와 평면좌표계에서 결과 비교)

  • Kang, Chul-Hyung;Han, Kyong-Won;Park, Hun-Hwee
    • Nuclear Engineering and Technology
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    • v.23 no.1
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    • pp.41-48
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    • 1991
  • Many of the analyses of the transient radionuclide migration are approximated by an one-dimensional geometry and/or planar geometry. To validate these approximations, one should prove that these are reasonable and proper approximations. In this paper, the approximation which was in the study of the transport through backfill into a fissure is tried to validate. In that analysis, a cylindrical geometry was approximated by a planar geometry. The numerical illustrations show that the planar approximation agrees very well with the result of the cylindrical geometry for a ratio of the backfill outer radius to the waste form radius closed to unity. Even for a larger ratio of the two radii, the numerical difference is relatively small. Also the planar approximation which was used in the analysis gives conservative estimates.

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PARAMETRIC INVESTIGATIONS ON THE DOUBLE DIFFUSIVE CONVECTION IN TRIANGULAR CAVITY

  • Kwon, SunJoo;Oh, SeYoung;Yun, Jae Heon;Chung, Sei-Young
    • Journal of the Chungcheong Mathematical Society
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    • v.20 no.4
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    • pp.419-432
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    • 2007
  • Double-diffusive convection inside a triangular porous cavity is studied numerically. Galerkin finite element method is adopted to derive the discrete form of the governing differential equations. The first-order backward Euler scheme is used for temporal discretization with the second-order Adams-Bashforth scheme for the convection terms in the energy and species conservation equations. The Boussinesq-Oberbeck approximation is used to calculate the density dependence on the temperature and concentration fields. A parametric study is performed with the Lewis number, the Rayleigh number, the buoyancy ratio, and the shape of the triangle. The effect of gravity orientation is considered also. Results obtained include the flow, temperature, and concentration fields. The differences induced by varying physical parameters are analyzed and discussed. It is found that the heat transfer rate is sensitive to the shape of the triangles. For the given geometries, buoyancy ratio and Rayleigh numbers are the dominating parameters controlling the heat transfer.

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Analysis of Detection Method for Series Arc Fault Signal by using DWT (이산 웨이블렛 변환을 이용한 직렬 아크고장 신호 검출 방법 분석)

  • Bang, Sun-Bae;Kim, Chong-Min;Park, Chong-Yeun;Chung, Young-Sik
    • The Transactions of the Korean Institute of Electrical Engineers P
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    • v.58 no.3
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    • pp.362-368
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    • 2009
  • Electrical fires have been occurred continuously in spite of installing ELB. Therefore the concern with the electrical arc-fault that cause the fire has growing. This paper measured series arc fault currents by the method of arc generator test in UL standard 1699. The used analysis methods in this paper are three different ways using DWT(discrete wavelet transform) those are frequently used for the arc fault current signal analysis. The arc fault detection probability is 100 % by method using noise-energy/shoulder-duration ratio of approximation coefficient. As these results, the variation of noise-energy and shoulder-duration ratio of approximation coefficient are founded important factors for the analysis of arc fault.

Intersymbol interference due to sampling-time jitter and its approximations in a raised cosing filtered system

  • 박영미;목진담;나상신
    • The Journal of Korean Institute of Communications and Information Sciences
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    • v.21 no.11
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    • pp.2942-2953
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    • 1996
  • This paper studies the effect of intersymbol interference due to sampling-time jitter on the worst-case bit error probability in a digital modultation over an additive white Gaussian noise channel, with the squared-root raised-cosine filters in the transmitter and the receiver. It derives approximation formulas using the Taylor series approximations. the principal results of this paper is the relationship between the worst-casse bit error probability, the degree of jitter, the roll factor of the raised cosine filter, and other quantities. Numerical results show, as expected, that the intersymbol interference decreases as the roll-off factor increases and the jitter decreases. They also show that the approximation formulas are accurate for smally intersymbol interference, i.e., for large roll-noise ratio $E_{b/}$ $N_{0}$.leq.7 dB and begin to lose accuracy for larger signal-to-noise ratio.o.o.

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Analysis of Phase Noise and HPA Non-linearity in the OFDM/FH Communication System (OFDM/FH 시스템에서 위상잡음과 비선형 HPA의 특성분석)

  • Li, Ying-Shan
    • Proceedings of the Korea Electromagnetic Engineering Society Conference
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    • 2003.11a
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    • pp.649-659
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    • 2003
  • OFDM/FH communication system Is widely used in the wireless communication for the large capacity and high-speed data transmission. However, phase noise and PAPR (peak-to-average power ratio) are the serious problems causing performance impairment. In this paper, PLL (phase locked loop) frequency synthesizer with high switching speed is used for the phase noise model. SSPA and TWTA are considered for the nonlinear HPA model. Under these conditions and by approximating $e^{j{\phi}[m]}$ into $1 + j{\phi}[m]-\frac{1}{2}{\phi}^2[m]$ for the phase noise nonlinear approximation, SINR (signal-to-interference-noise-ratio) with nonlinear HPA and phase noise is derived in the OFDM/FH system. The bit error probabilities (BER) are found by computer simulation method and semi-analytical method. The simulation results closely match with the semi-analytical results.

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Plow Analysis for Radiating Fluid with Density Variation affected by Overheat Ratio (과열비에 따른 유체밀도 변화를 고려한 복사유체 유동 해석)

  • Han C. Y.;Chae J. W.;Park E. S.;Nam M. G.
    • 한국전산유체공학회:학술대회논문집
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    • 2005.04a
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    • pp.75-78
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    • 2005
  • A numerical investigation has been performed to discuss the radiation-affected steady-laminar natural convection in an enclosure under a large temperature difference. Due to inherent nature of this study, the Boussinesq approximation is no longer valid. Therefore the radiating fluid in an enclosure is treated as a ideal gas. To examine the effects of thermal radiation on thermo-fluid dynamic behaviors in complex geometries, two incomplete partitions are introduced. Based on the results of this study, the dispositions of incomplete partitions with radiatively participating medium are found to incur a distinct difference in fluid-dynamic as well as thermal behavior.

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Determination of Wave Run-up Height on S-berm Breakwater (복합사면에서의 도파고 산정)

  • 유동훈;이대석
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.13 no.3
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    • pp.202-208
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    • 2001
  • Explicit approximation has been developed to estimate the run-up height on S-berm breakwater on the basis of Saville's hypothetical slope method. For the explicit expression of run-up height several relations are developed to represent the ratio of run-up height against breakwater slope with various conditions of water depth and wave steepness. For the verification of explicit approximation the results are compared with Saville's measurement data and simple expression of Delft Hydraulic Laboratory.

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Investigation on fluid-particle velocity double correlation in fluid- particle two-phase turbulent flows (유체에 입자가 부상된 2상난류운동에서 유체-입자속도 2차상관관계에 관한 연구)

  • 양선규;최영돈
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.12 no.6
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    • pp.1438-1449
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    • 1988
  • An analysis of radiative heat transfer has been conducted on axisymmetric finite cylindrical media. It is assumed that the temperature in the media is uniformly distributed and the boundaries are diffusely emitting and reflecting at a constant temperature. The scattering phase function is represented by the delta-Eddington approximation to account for highly forward scattering by particulates just as in the combustion system. Exact numerical solutions are obtained by Gaussian quadrature method and compared with P-1 and P-3 approximation solutions to verify their engineering application limit. The effects of optical thickness, scattering albedo, wall emissivity and aspect ratio are investigated. The results show that P-3 approximation is found to be in good agreement with the exact solution.

Structural Design of Piezoelectric Actuator Considering Polarization Direction and Continuous Approximation of Material Distribution (분극방향과 재료분포의 연속적 근사방법을 고려한 압전형 액추에이터의 구조설계)

  • Lim, Young-Seok;Yoo, Jeong-Hoon;Min, Seung-Jae
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.30 no.9 s.252
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    • pp.1102-1109
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    • 2006
  • In this paper, the polarization of piezoelectric materials is considered to improve actuation since the piezoelectric polarization has influences on the performance of the actuator. The topology design of compliant mechanism can be formulated as an optimization problem of material distribution in a fixed design domain and continuous approximation of material distribution (CAMD) method has demonstrated its effectiveness to prevent the numerical instabilities in topology optimization. The optimization problem is formulated to maximize the mean transduction ratio subject to the total volume constraints and solved using a sequential linear programming algorithm. The effect of CAMD and the performance improvement of actuator are confirmed through Moonie actuator and PZT suspension design.

Numerical Analysis in Heat Transfer of a Triangular Fin (삼각휜 열전달의 수치해석)

  • Chun, Sang-Myung;Kwon, Young-Pil
    • The Magazine of the Society of Air-Conditioning and Refrigerating Engineers of Korea
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    • v.11 no.3
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    • pp.52-57
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    • 1982
  • One-dimensional approximation for fin problems is widely used in current texts and industrial practice. The errors caused by this approximation is analysed for a longitudinal triangular fin by the numerical solution of two-dimensional fin equation. Two-dimensional solution is obtained by the finite element method and com pared with the one-dimensional esact solution. The results show that total heat transfer and fin efficiency are overestimated by the one-dimensional approximation. The factors which cause these errors are the Biot number (Bi) and the ratio of fin length to half the thickness (L/a). When Bi is smaller than 1.0 these errors are smaller than $10\%$, but when Bi is larger than 5.0 they are a few ten percents. Fin efficiency obtaned by one-dimensional and long fin assumption is valid only then Bi is small and L/a is large.

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